There has been a long felt need for a treatment system and method for tattoos, for tattoo procedures, etc. that is effective without the undesirable side effects of the prior art. There is no universally accepted tattoo treatment. Laser phototherapy (photothermolysis) is perhaps the best treatment regimen available to date for tattoo lightening and removal.
Physicians often use laser phototherapy involving lasers operating at a variety of wavelengths and power and fluence levels. Some physicians prefer Q-switched Nd:YAG lasers operating at 1064 nm. Others prefer typically Q-switched alexandrite lasers operating at 755 nm. Still others prefer dye lasers operating in the visual portion of the spectrum, or, for example, frequency doubled Nd:YAG lasers operating at 532 nm, sometimes described as “KTP lasers”, KTP being the crystal which doubles the frequency of the laser. Many other laser types and wavelengths have been used in tattoo procedures as well.
While some favorable treatment results have been achieved, no treatment regimen is without problems. For example, full thickness burns that leave permanent scars have been observed as adverse events following laser phototherapy. Thus, although various devices and techniques have been used, none so far have proven significantly effective.
One reason for problems or adverse events in tattoo treatment may relate to the unpredictable nature of the thermal conversion of oxyhemoglobin (HbO2) and deoxyhemoglobin (RHb) into methemoglobin (metHb). metHb has a much higher optical absorption relative to HbO2 or rHb in the near infrared (NIR) portion of the spectrum thus facilitating thermal runaway once conversion has started. This unpredictable, pseudo-instantaneous conversion is of particular concern in connection with the use of NIR light (i.e., the NIR portion of the spectrum (e.g., around 1064 nm)), which is otherwise desirable for use since NIR light penetrates more deeply into the treatment site than visible light. Use of NIR light thus may permit tattoo treatment to a greater depth, which may result in a better outcome as more of the area or volume including the tattoo portion to be treated can be treated at one time. Prior systems and methods simply are not significantly effective in controlling the thermal conversion of HbO2 and RHb into metHb.
Another reason for adverse events in tattoo treatment using prior systems and methods may be the unpredictable nature of the treatment site. At all wavelengths, including the isosbestic point between HbO2 and RHb (approximately 810 nm), the optical absorption of the blood in the vessels can significantly change in the course of a Q-switched or similar laser pulse. In practical terms, a pulse that is perfectly well tolerated in one location or tattoo portion may induce adverse effects (e.g., burning, scarring, pain, hypopigmentation, hyperpigmentation) in another nearby location or portion. This is because the local scattering, absorption, and/or other properties proximate to the tattoo may change from site to site, which contributes to the uncertainty of the extent of photothermal conversion of HbO2 and RHb into metHb from site to site. Blood treated in the vasculature at one location proximate the tattoo may thermally convert into metHb to a different extent than blood in the vasculature in a different location proximate the tattoo.
A somewhat similar yet separate reason for adverse events in tattoo procedures using prior systems and methods may relate to an unacceptably low level of treatment repeatability. Unwanted uncertainty and results stem from the unpredictability associated with optical and physiological differences across patients. Every patient, every tattoo, etc. is different. An effective set of treatment parameters in one patient may unexpectedly cause an adverse event in another patient with a seemingly identical tattoo or condition. Prior systems and methods simply lack a desired robustness in that they are not significantly effective in controlling factors, e.g., the thermal conversion of HbO2 and RHb into metHb, across individual patients in a treatment group.
One problem, then, in a particular aspect may be viewed as an optical “runaway” effect. Prior systems and methods may be unattractive because this adverse event may occur, for example, as the laser used in treatment is gradually increased in power and/or fluence. As photothermal conversion of one or more hemoglobin species into metHb occurs, suddenly a small change in one or more laser operating parameters or one or more treatment conditions may have a grossly larger effect due to the new presence of metHb. As one example, variations in pressure that the physician applies to a laser hand piece may induce varying degrees of exsanguination, altering the optical properties of a treatment area, and confounding predictability of photothermal conversion. Purpura can result from this effect as well.
Differences in the types of tattoos treated also results in problematic outcomes. Certain tattoo colors (e.g., yellow, green, brown) typically are difficult to treat as compared to other colors (e.g., black) using prior approaches. There is no significantly effective prior system and method applicable to the wide variety of tattoo colors (including difficult to treat colors).
Another problem associated with prior art tattoo procedures is that often such procedures are messy. Typically, debris is ejected from a treatment site, e.g., during laser use. The debris may be solids, liquids, gases, aerosols, and/or other forms of ejecta. Also, with some patients, a treating clinician may be exposed as a result to an unacceptable risk of exposure, e.g., to HIV, hepatitis-C, and/or other infectious diseases. There is no significantly effective prior system and method to help control such ejecta and reduce such adverse risks.
Another problem associated with prior art tattoo procedures may stem from treatment side effects. By way of example, during a laser treatment session, exposure of a treatment area to a laser output may create one or more conditions within the treatment area that tend to reduce the effectiveness of subsequent laser exposures. One example of such side effects is a “whitening” of the area treated.
During tattoo treatment, a “whitening” reaction typically occurs, as evidenced by the formation of bubbles, e.g., in the dermis. The whitening reaction typically occurs immediately upon first laser exposure, with results of the reaction remaining during and after subsequent laser exposures in the same session. The whitening reaction may include, result in, or be caused by, the generation of bubbles or other factors, e.g., due to rapid heating or energy transfer associated with laser exposure, due to laser-induced shock waves, due to microscopically “explosive” cell or other reactions, due to two photon processes (e.g., associated with use of a picosecond or faster laser), etc.
The “bubbles” associated with whitening may be micro-cavitation bubbles and/or other events and/or circumstances capable of having similar or other negative therapeutic effects, e.g., attenuation of light, light scattering, etc. For convenience only, and without limitation, such bubbles and/or other events and/or circumstances shall be referred to herein individually and collectively as a “bubble” or “bubbles.”
Bubbles generally may be located in an area or volume including a portion of the dermis, although other locations are possible too. The bubbles generally may be located in an area or volume including a portion of skin. Heating may be localized, and/or may produce or otherwise cause or promote localized bubble generation. Typically, tissue, skin, tattoo pigment, the dermis portion, etc. are heated during treatment.
It has been observed that a whitening reaction may fade over about twenty minutes or more following the last laser exposure. Such fading may be evidenced by the dissolving of bubbles including gas, or by other factors associated with bubble reduction. Resolution of the whitening reaction may be caused at least in part by the cooling of one or more heated portions.
Whitening is problematic at least in part because the presence of bubbles in the treatment area from a first laser pass may attenuate or weaken the delivery of light in one or more subsequent laser passes. For instance, light impinging on bubbles may scatter in multiple directions, including away from the treatment area. Thus, bubble presence reduces light therapy effectiveness.
Typically, clinicians in tattoo procedures may avoid in part some of the adverse consequences of whitening simply by waiting for the unwanted whitening condition to resolve naturally. Where such a therapy session includes, for example, four laser passes, the total session treatment time (i.e., length of session) may equal about 60-80 minutes or more.
Treatment time, then, often is quite problematic. Typically, prior art tattoo treatment includes, among other things, a single treatment session including multiple (e.g., up to four) laser exposures to a treatment area, with an interval of twenty minutes or more between laser exposures. See, e.g., Kossida et al, Optical tattoo removal in a single laser session based on the method of repeated exposures, J. Am. Acad. Dermatology 2012 feb 66(2): 271-7. Such lengthy treatment time often poses significant problems for patients and clinicians alike. Both clinicians and patients generally would prefer shorter treatment times as compared to such extended periods. This is especially true when multiple treatment sessions are required over a period of months to achieve desired results.
Thus, what is needed is an improved method and system for tattoo treatment that helps predictably and effectively treat tattoos while controlling, reducing, minimizing, and/or eliminating one or more of: (i) the optical “runaway” effect, (ii) system operating or treatment parameter uncertainties, and (iii) one or more other disadvantages that may be associated with prior art systems and methods for treating tattoos (e.g., whitening, attenuation, lengthy treatment times, etc.).